It is known in the art that a silicon-containing polysulfide polymer which contains in its molecule repeating units represented by the formula (SzR9)k (where “z” is a number greater than and equal to 1, R9 is a divalent organic group, and “k” is a number greater than and equal to 1 is used as an additive that improves properties of a dyene-type rubber composition for molding tires, rubber rolls, or similar products. For example, Japanese Patent Application Publication (hereinafter referred to as Kokai) H9-3248 (equivalent to U.S. Pat. No. 5,827,912) describes synthesis of a silylated polysulfide polymer from a mercaptosilane, dithiol, and sulfur dichloride in the presence of a non-aqueous solvent, as well as synthesis of a silylated polysulfide from a silylated halogenated alkyl, dihalogenated alkyl, and a metal sulfide in the presence of a non-aqueous solvent. However, these methods are associated with a number of problems such as generation of a toxic gaseous hydrochloride, conduction of reactions under completely anhydrous conditions, consumption of large quantities of solvents, and difficulties in connection with separation of the by-product metal halides, due to increasing viscosity of the product.
Furthermore, Kokai H10-120788 and Kokai H10-139939 describe synthesis of silyl-capped polysulfide polymers through an addition reaction between a mercapto-capped polysulfide polymer and an epoxysilane and synthesis of a silyl-capped polysulfide through an addition reaction between a polysulfide polymer end-capped with hydroxyl groups and an isocyanate silane. However, the addition reaction between the mercapto-capped polysulfide polymer and an epoxysilane is accompanied by gelation caused by hydroxyl groups, which are formed after the addition reaction between the mercapto groups and epoxy groups. Another unfavorable factor is that the above processes have low efficiency as they require a two-stage reaction that requires addition of sulfur in the presence of an alkali catalyst after introduction of alkoxysilyl groups resulting from the aforementioned addition reaction and adjustment of a sulfur number in sulfide groups. On the other hand, the addition reaction between the isocyanate silane and the polysulfide polymer having molecular terminals capped with hydroxyl groups also encounters a number of problems. These problems are the following: instability caused by a concurrent condensation reaction that occurs simultaneously with the addition reaction between the hydroxyl groups on the terminals of the polysulfide polymer and alkoxy groups contained in the isocyanate silane; high cost of the isocyanate silane; and low reaction efficiency resulting from the necessity of using the same adjustment of the sulfur number as in the addition reaction after introduction of alkoxysilyl groups generated, in this case, in the aforementioned condensation reaction.
Kokai 2000-63521 discloses synthesis of a polysulfide polymer end-capped with silyl groups by causing an addition reaction between a vinyl silane and a polysulfide polymer having on its molecular terminals mercapto or hydroxyl groups. The problem associated with this method is that the process has low efficiency as it requires a two-stage reaction with addition of sulfur in the presence of an alkali catalyst after introduction of silyl groups resulting from the aforementioned addition reaction between the vinyl silane and polysulfide polymer with subsequent adjustment of sulfur number in sulfide groups.